Industrial process industries primarily rely upon energy sources that include one or more combustion processes. Such combustion processes include operation of a furnace or boiler to generate energy from combustion, which is then used for the process. While combustion provides relatively low-cost energy, its use is typically regulated and combustion efficiency is sought to be maximized. Accordingly, one goal of the process management industry is to reduce the cost of fuel being burned, which also inherently minimizes production of greenhouse gases by maximizing combustion efficiency of existing furnaces and boilers.
In situ or in-process analyzers are commonly used for monitoring, optimizing, and/or controlling combustion processes. Typically, these analyzers employ sensors that are heated to relatively high temperatures and are operated directly above, or near, the furnace or boiler combustion zone. Known analyzers, such as those sold under the trade designation Oxymitter or Model 6888 O2 Combustion Flue Gas Transmitter available from Rosemount Analytical, Inc. of Solon, Ohio (an Emerson Process Management company), often employ zirconia oxide sensors heated to a temperature above approximately 736° Celsius (1300° Fahrenheit). If the combustion process should suffer a flame out condition, raw fuel and air are could be exposed to this sensor which, by virtue of its elevated temperature, could become an ignition source with the possibility of precipitating an explosion.
Some process analyzers are approved for hazardous area operation. Some approvals include those provided by the Canadian Standards Association (CSA), Factory Mutual (FM), ATEX, et cetera. Typically, hazardous area-approved analyzers include a flame arrestor that is added over the diffuser with the intent of quenching, or otherwise inhibiting, an explosion that might occur in front of the heated measurement cell, thereby preventing the ignition of the larger fuel volume in the boiler or combustion zone. These flame arrestors have been tested and approved in the past. However, it is believed that such arrestors can be improved. Moreover, the utilization of the flame arrestors may inhibit, to some degree, access to the measurement cell thereby increasing measurement lag. However, the utilization of flame arrestors adds expense and complexity to the system.
Some known process analyzers use flame scanners to detect a flameout and quickly and automatically cease fuel and/or air flow. Additionally, some efforts have been directed toward automatically creating a gaseous buffer between the measurement cell and the flue upon detection of a flameout. While these systems are effective, they add additional hardware and complexity thereby increasing system cost.